The objective of the research is to develop technology that will facilitate the regeneration of heart, lung, and other cell types from somatic stem cells. Although multipotent cells are known to reside within numerous adult tissues, their limited proliferative and differentiative capacities constrain their use for regenerative therapies. Prospects for improving efficacy of contribution to target tissue will be facilitated by molecular genetic-level knowledge of the factors that regulate differentiation. To date, differentiation of somatic stem cells has been evaluated primarily in whole animal models of tissue damage. Since whole animal models are not readily conducive for the discovery of genes and proteins that regulate differentiation, this application proposes four aims to design and use in vitro, culture assays to identify molecular regulators of somatic stem cell differentiation. Emphasis will be placed on, but not limited, to cardiomyocyte differentiation. The first two aims will design culture assays to evaluate differentiation of a promising somatic stem cell population (known as SP cells) that can be FACS enriched from a range of differentiated tissues, including heart. Aim 1 will evaluate whether factors and tissues that promote embryonic cardiomyogenesis stimulate these cells to differentiate. Preliminary data describe interspecies tissue recombination assays to evaluate differentiation in vitro. Similarly, aim 2 will test the hypothesis that differentiated myocardium provides factors that promote differentation. Aims 3 and 4 are to design moderate to high throughput assays for the identification of synthetic and natural modulators of differentiation. Aim 3 will define molecular markers of the somatic stem cell to cardiomyocyte differentiation process that will be used as endpoints in these assays. Aim 4 will establish the mechanics of small molecule screens and carry out pilot screens. To carry out Aim 4 concurrently with the other aims, embryonic stem cells will be used initially as they proliferate well in culture and differentiate into cardiomyocytes in response to known inducers (preliminary data).